# How-To: Java isDigit() Character function

Sometimes it is helpful to know if a character is a digit (`0`-`9`) or not.

The Java built-in Character class provides an `isDigit()` function that determines if a character is a digit or not.

Here is an example. First, here are two character values to test:

```java
char c1 = '9';
char c2 = 'A';
```

The `c1` variable contains a `char` value that is a digit. The `c2` variable contains a `char` value that is not a digit.

To invoke the `isDigit()` function, use the `Character` class and pass in the character as the parameter. The return value is a `Boolean` (`true` or `false`) value.

So, to check if the `c1` variable is a digit and output the result:

```java
System.out.println( Character.isDigit(c1) ); // true
```

This function call returns `true`, since the character `'9'` is a digit. The code outputs `true`.  Note that the function call is inside the `println()` method as its parameter.

The same process checks the `c2` variable:

```java
System.out.println( Character.isDigit(c2) ); // false
```

This time, the output is `false`, since `'A'` is not a digit.

Here is the complete program:

```java
public class Example {
  public static void main(String[] args) throws Exception {
    
    char c1 = '9';
    char c2 = 'A';

    System.out.println( Character.isDigit(c1) ); // true
    System.out.println( Character.isDigit(c2) ); // false

  }
}
```

The `Character.isDigit()` function is very useful when determining if a character is a digit or not. This can help with a variety of string processing tasks in the programs you write.

Thanks for reading. 😃

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